1. Field of the Invention
The present invention relates to an apparatus for and a method of processing a glass optical fiber drawn from an optical fiber preform when drawing an optical fiber while fusing by heating and pulling by a pulling mechanism one end of the optical fiber preform and to a method of manufacturing and a method of drawing an optical fiber.
2. Description of the Related Art
An optical fiber is manufactured by fusing by heating one end of an optical fiber preform made of glass in a draw heating furnace, drawing a glass optical fiber from the one end, and forming a coating made of a resin or the like around the drawn glass optical fiber using a die or the like. The manufactured optical fiber is wound up by a winding machine via a capstan roller.
However, a leading end of the optical fiber preform may have a ratio between an external diameter of a core portion and an external diameter of a cladding portion, which does not meet a standard ratio. Because a core diameter and a cladding diameter of a glass optical fiber drawn from such a leading end do not meet standard diameters, the glass optical fiber cannot be used as a product. Therefore, the leading end of the optical fiber preform has been used in drawing for adjusting various drawing conditions when starting a process of manufacturing an optical fiber, and that drawn glass optical fiber has been discarded.
Japanese Patent Application Laid-open No. H10-330133 discloses a method of processing a leading end of an optical fiber preform that cannot be used as a product and should be discarded. In this method, the leading end of the optical fiber preform is processed using a processing apparatus including a pulling mechanism for pulling a glass optical fiber having an external diameter larger than a product-to-be optical fiber, a cutting mechanism for cutting the pulled glass optical fiber having the large external diameter, and an accommodating mechanism for accommodating the cut glass optical-fiber pieces.
However, since the above processing apparatus includes the pulling mechanism independent from a pulling mechanism for manufacturing the optical fiber, the apparatus becomes large. Further, because the glass optical fiber is processed while having the large external diameter, the processing apparatus needs to be arranged as directly below the draw heating furnace for the glass optical fiber as possible to perform the processing. As a result, a troublesome process has been required, in which a coating unit arranged below a draw heating furnace in a general apparatus for manufacturing an optical fiber is moved away once, a processing apparatus is arranged instead, a glass optical fiber is drawn and processed, the drawing of the glass optical fiber is stopped after the processing, the coating unit is returned to the original location, and an optical fiber is manufactured. Further, with the increase in the drawing speed, there has been a risk that a glass optical fiber at a high temperature and not sufficiently cooled down might enter the processing apparatus, damaging the processing apparatus.
There may also be a method of drawing and forming a coating, similarly to normal optical fibers, around a leading end of an optical fiber preform to be processed and winding up by a winding mechanism, without using the above processing apparatus. However, this method has a problem of consuming an extra amount of the coating material for the discarded optical fiber. Further, if a glass optical fiber is drawn without a coating formed thereon, because the glass optical fiber is very fragile and broken easily, the glass optical fiber cannot be wound up by a winding mechanism and processing becomes difficult.